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EVOLUTION
Chapter 13.1
Charles Darwin
Darwin’s Theory of Evolution
◼ Evolution, or change over time, is the process by
which modern organisms have descended from
ancient organisms.
◼ A scientific theory is a well-supported testable
explanation of phenomena that have occurred in
the natural world.
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Who was Charles Darwin?
◼ Son of Robert Darwin (physician); grandson of
Erasmus Darwin (physician)
◼ Was to study medicine, stomach not strong
enough
◼ Studied theology, loved natural science
Not testable
Voyage of the Beagle
Voyage of the Beagle
◼ Dates: February 12th, 1831
◼ Captain: Charles Darwin
◼ Ship: H.M.S. Beagle
◼ Destination: Voyage around the world
◼ Original purpose: Collect evidence to support
biblical account of creation
Not testable
Patterns of Diversity
◼ Darwin visited Argentina (left pic) and Australia
(right) which had similar grassland ecosystems
◆ Grasslands were inhabited by very different animals
◆ Neither Argentina nor Australia was home to the
sorts of animals that lived in European grasslands
Patterns of Diversity
◼ Darwin posed challenging
questions.
◆ Why were there no rabbits in
Australia, despite the presence
of habitats that seemed perfect
for them?
◆ Why were there no kangaroos
in England?
Living Organisms and Fossils
◼ Darwin collected the preserved remains of ancient
organisms, called fossils
◼ Some of those fossils resembled organisms that were
still alive today
◼ Others looked completely unlike any creature he had
ever seen
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Living Organisms and Fossils
◼ As Darwin studied fossils, new questions arose.
◆ Why had so many of these species disappeared?
◆ How were they related to living species?
Fossils
For more info, see ch 13-3. Not testable (review from science 10).
The Galapagos Islands
The Galapagos Islands
◼ The smallest, lowest islands
were hot, dry, and nearly
barren (e.g. Hood Island-
sparse vegetation
◼ The higher islands had
greater rainfall and a different
assortment of plants and
animals (e.g. Isabela Island
had rich vegetation)
The Galapagos Islands
◼ Darwin was fascinated in particular by the land tortoises and marine iguanas in the Galapagos
◼ Giant tortoises varied in predictable ways from one island to another
◼ The shape of a tortoise's shell could be used to identify which island a particular tortoise inhabited
Animals found in the GalapagosLand Tortoises Darwin’s Finches
Blue-Footed Booby Marine Iguanas
The Journey Home
◼ Darwin analysed the specimens he had collected
and observations he had made
◼ Darwin observed that characteristics of many
plants and animals vary greatly among the islands
◆ Many observations contradicted creationism
◼ Hypothesis (based on his evidence): Separate
species may have arisen from an original ancestor
◆ Wrote an essay with his findings but did not publish for
20 years for fear of being discredited as a scientist
Key Notes from “Fitness: To
Survive and Reproduce” (13-1)
◼ Fitness: the physical traits and behaviours
that enabled organisms to survive and
reproduce in their environment
Key Notes from “Fitness: To
Survive and Reproduce” (13-1)
Discuss:
◼ Broadly, what might affect an organism’s
fitness? (e.g. ability to ______?)◆ Attract mates, look after offspring, fertility
◆ Find/extract/digest food
◆ Work together with social group or symbiotic partner
◆ Hide from predators (camouflage, running, etc)
◆ Regulate body temperature
◆ Use resources efficiently
◆ And more!!
Key Notes from “Fitness: To
Survive and Reproduce” (13-1)
Discuss:
◼ What is one trait that affects the fitness of
humans? Maple trees? Domestic dogs?
◼ What would happen to an organism’s
fitness if the environment changes? Think
of specific examples.
Key Notes from “Fitness: To
Survive and Reproduce” (13-1)
◼ Darwin’s argument: new organisms come
from pre-existing organisms, and each
species has descended from other species
over time
◼ Principle of common descent:
◆All species have shared/common
ancestors
Common misconception: Humans are not
descended from apes. We are simply relatives
descended from a common ancestor.
What the common
ancestor of
chimpanzees &
humans may have
looked like
Key Notes from “Fitness: To
Survive and Reproduce” (13-1)
◼ Adaptation: process of changes that allow
an organism to be:
◆Better suited to its environment
◆Better able to survive and reproduce
◆= inherited characteristics that increases
an organism’s fitness for survival
Key Notes from “Fitness: To
Survive and Reproduce” (13-1)
Discuss:
◼ How are fitness and adaptations similar?
Different? Add to your notes.
◆ Similar: both linked to ability to survive and
reproduce in environment; can be inherited; can
refer to individual organisms or larger groups
(e.g. species)
◆ Different: fitness is the overall ability to survive
and reproduce; adaptations are the traits that
increase fitness.
Key Notes from “Fitness: To
Survive and Reproduce” (13-1)
James Hutton:
◼ 1795 Theory of Geological change
◆ Geological changes occur slowly over time through natural processes
◆ Earth is very old: much older than thousands of years
Darwin’s Inspirations/Influences
Charles Lyell:
◼ Book: Principles of Geography
◼ Geographical features can be built up or torn down
◼ Darwin: if earth changed over time, what about life?
Darwin’s Inspirations/Influences
Jean Baptiste Lamarck
(1744-1829)
◼ French naturalist
◼ First to come up with a theory of evolution
◆ Organisms change during their lifetimes to
‘adapt’ to environment
⧫ Desire to change
⧫ Use and disuse
◆ Changes are inherited by offspring; change takes
place gradually and constantly
Darwin’s Inspirations/Influences
Lamarck: Use and disuse
Further reading:
https://www.sparknotes.com/biology/evolution/lamarck/section2/
◼ Parts of organism that are used most often
will become more developed, specialized
for environment
◆ (Similar to everyday use of “adaptations”)
◼ Parts of organism that are not used will be
underdeveloped or disappear
◆ (Similar to “vestigial structures”…stay tuned!)
Darwin’s Inspirations/Influences
https://www.sparknotes.com/biology/evolution/lamarck/section2/
Lamarck: Use and disuse
Further reading:
https://www.sparknotes.com/biology/evolution/lamarck/section2/
Darwin’s Inspirations/Influences
https://www.sparknotes.com/biology/evolution/lamarck/section2/
Lamarck: Use and disuse
Further reading:
https://www.sparknotes.com/biology/evolution/lamarck/section2/
https://www.sparknotes.com/biology/evolution/lamarck/section2/
Lamarck: Use and disuse
Further reading:
https://www.sparknotes.com/biology/evolution/lamarck/section2/
https://www.sparknotes.com/biology/evolution/lamarck/section2/
Population Growth
◼ Population too large to
be supported by
resources
◼ Plan: eliminate half of
humans; restore
balance
Thanos from Avengers: Infinity War
Not testable
Darwin’s Inspirations/Influences
Population Growth
◼ Thomas Malthus-19th century English economist
◼ When human population increases, competition for resources (food, space) occurs
◼ Struggle for existence: population limited by food, war, disease
◼ Not all survive and reproduce
Darwin’s Inspirations/Influences
Publication of Origin of Species
◼ Russel Wallace and Darwin
co-authored a paper on
natural selection (1858)
◼ Darwin published Origin of
Species (1859) → public
recognition
Artificial Selection
Artificial Selection
Artificial Selection
1. Variation exists in the population
◆Natural
⧫Cannot be caused by farmers*
⧫Occurs randomly through mutation
◆Can be inherited by offspring
*Exception: GMOs, irradiation
Artificial Selection
2. Farmers select traits they like from the
variation presented. Only individuals with
those traits are allowed to produce offspring.
Artificial Selection
3. Over many generations, the preferred
trait(s) increase in frequency.
Natural Selection
1. Variation exists in the population
◆Natural
⧫Occurs randomly through mutation
◆Can be inherited by offspring
Natural Selection
2.
Struggle for existence: individuals in a
constant struggle for life against environment
and each other (think Malthus)
Survival of the fittest: some traits are better-
suited: these individuals survive and
reproduce (more).
Natural Selection
3. Over many generations, adaptations
increase in frequency in the population.
Evolution occurs.
Remember: variation (and thus, adaptations) can be either physical or behavioural!
Natural Selection vs Evolution
◼ Individual level
◼ Who is more adapted
to environment? Who
survives to reproduce?
Lifespan-based
◼ Population level
◼ Change in
population’s traits
over many generations
Case Study: Peppered Moths
1. Variation exists
in the population
Biston betularia f. typica
Biston betularia f. carbonaria
Case Study: Peppered Moths
2. Natural
Selection
occurs (white
moths
selected
against)
Case Study: Peppered Moths
3. Evolution occurs. Frequency of dark moths
increases; frequency of white moths decreases.
Case Study: Peppered Moths
Experiment:◼ H.B.D. Kettlewell
(British Ecologist)
◼ Tagged moths
◼ Released into agricultural
and industrial areas
◼ Re-captured: how many
survived?
◼ Findings: more light-coloured
moths survived in agricultural;
more dark-coloured in industrial
◼ Conclusion: moth population had evolved through natural selection